code: def __len__(self):
      return len(self.bert_inputs)
  
imports: import json
  import torch
  from torch.utils.data import Dataset
  from torch.nn.utils.rnn import pad_sequence
  import numpy
  import prettytable
  from tqdm import tqdm
  from transformers import AutoTokenizer
  import os
  from deepke.name_entity_re.standard.tools import *
  import requests
  from typing import List
  from .utils import convert_index_to_text
label_desc: Use image node_id 3 for calling the RelationDataset obj's underlying member method code with example usage: obj.__len__() and returns: len